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<A NAME="PCILU"><H1>PCILU</H1></A>
Incomplete factorization preconditioners.
<H3><FONT COLOR="#CC3333">Options Database Keys</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_ilu_levels <k> </B></TD><TD>- number of levels of fill for ILU(k)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_ilu_in_place </B></TD><TD>- only for ILU(0) with natural ordering, reuses the space of the matrix for
its factorization (overwrites original matrix)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_ilu_diagonal_fill </B></TD><TD>- fill in a zero diagonal even if levels of fill indicate it wouldn't be fill
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_ilu_reuse_ordering </B></TD><TD>- reuse ordering of factorized matrix from previous factorization
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_ilu_damping </B></TD><TD>- add damping to diagonal to prevent zero (or very small) pivots
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_ilu_shift </B></TD><TD>- apply Manteuffel shift to diagonal to force positive definite preconditioner
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_ilu_zeropivot <tol> </B></TD><TD>- set tolerance for what is considered a zero pivot
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_ilu_use_drop_tolerance <dt,dtcol,maxrowcount> </B></TD><TD>- use Saad's drop tolerance ILUdt
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_ilu_fill <nfill> </B></TD><TD>- expected amount of fill in factored matrix compared to original matrix, nfill > 1
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_ilu_nonzeros_along_diagonal </B></TD><TD>- reorder the matrix before factorization to remove zeros from the diagonal,
this decreases the chance of getting a zero pivot
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_ilu_mat_ordering_type <natural,nd,1wd,rcm,qmd> </B></TD><TD>- set the row/column ordering of the factored matrix
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_ilu_pivot_in_blocks </B></TD><TD>- for block ILU(k) factorization, i.e. with BAIJ matrices with block <A HREF="../Sys/size.html#size">size</A> larger
than 1 the diagonal blocks are factored with partial pivoting (this increases the
stability of the ILU factorization
</TD></TR></TABLE>
<P>
<P>
<P>
Notes: Only implemented for some matrix formats. Not implemented in parallel
<P>
For BAIJ matrices this implements a point block ILU
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../PC/PCCreate.html#PCCreate">PCCreate</A>(), <A HREF="../PC/PCSetType.html#PCSetType">PCSetType</A>(), <A HREF="../PC/PCType.html#PCType">PCType</A> (for list of available types), <A HREF="../PC/PC.html#PC">PC</A>, <A HREF="../PC/PCSOR.html#PCSOR">PCSOR</A>, <A HREF="../Mat/MatOrderingType.html#MatOrderingType">MatOrderingType</A>,
<BR>PCILUSetSetZeroPivot(), <A HREF="../PC/PCILUSetDamping.html#PCILUSetDamping">PCILUSetDamping</A>(), <A HREF="../PC/PCILUSetShift.html#PCILUSetShift">PCILUSetShift</A>(), <A HREF="../PC/PCILUSetUseDropTolerance.html#PCILUSetUseDropTolerance">PCILUSetUseDropTolerance</A>(),
<A HREF="../PC/PCILUSetFill.html#PCILUSetFill">PCILUSetFill</A>(), <A HREF="../PC/PCILUSetMatOrdering.html#PCILUSetMatOrdering">PCILUSetMatOrdering</A>(), <A HREF="../PC/PCILUSetReuseOrdering.html#PCILUSetReuseOrdering">PCILUSetReuseOrdering</A>(), <A HREF="../PC/PCILUDTSetReuseFill.html#PCILUDTSetReuseFill">PCILUDTSetReuseFill</A>(),
<A HREF="../PC/PCILUSetLevels.html#PCILUSetLevels">PCILUSetLevels</A>(), <A HREF="../PC/PCILUSetUseInPlace.html#PCILUSetUseInPlace">PCILUSetUseInPlace</A>(), <A HREF="../PC/PCILUSetAllowDiagonalFill.html#PCILUSetAllowDiagonalFill">PCILUSetAllowDiagonalFill</A>(), <A HREF="../PC/PCILUSetPivotInBlocks.html#PCILUSetPivotInBlocks">PCILUSetPivotInBlocks</A>(),
<P>
<P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>beginner
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/ksp/pc/impls/ilu/ilu.c.html#PCILU">src/ksp/pc/impls/ilu/ilu.c</A>
<BR><A HREF="./index.html">Index of all PC routines</A>
<BR><A HREF="../../index.html">Table of Contents for all manual pages</A>
<BR><A HREF="../singleindex.html">Index of all manual pages</A>
<P><H3><FONT COLOR="#CC3333">Examples</FONT></H3>
<A HREF="../../../src/ksp/pc/examples/tutorials/ex1.c.html">src/ksp/pc/examples/tutorials/ex1.c.html</A><BR>
<A HREF="../../../src/ksp/examples/tutorials/ex7.c.html">src/ksp/examples/tutorials/ex7.c.html</A><BR>
<A HREF="../../../src/ksp/examples/tutorials/ex8.c.html">src/ksp/examples/tutorials/ex8.c.html</A><BR>
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